1/4 pound blue cheese, preferably Maytag, crumbled (3/4 cup)
1 head iceberg lettuce, cut into 1-inch pieces
1/2 small red onion, thinly sliced
1 celery rib, thinly sliced
Preheat the oven to 350°. On a baking sheet, toss the bread cubes with 1 tablespoon of the vegetable oil and toast for 15 minutes, stirring once or twice, until the bread is golden and crisp.
Meanwhile, in a large skillet, cook the bacon over moderately high heat, turning once, until crisp, about 6 minutes. Drain on paper towels and crumble.
In a small bowl, using the back of a spoon, mash the garlic to a paste with a pinch of salt. Whisk in the mayonnaise, buttermilk, vinegar and mustard. Gradually whisk in the remaining 1/2 cup of vegetable oil and season with salt and cayenne. Stir in the blue cheese.
In a large bowl, toss the lettuce, onion, celery, bacon and croutons with the dressing and serve right away.
The bacon and dressing can be refrigerated separately overnight. The croutons can be stored overnight in an airtight container.